Cutting through the Paleo hype: The evidence for the Palaeolithic diet

Background

General practitioners (GPs) are commonly asked about popular diets. The Palaeolithic diet is both highly popular and controversial.

Objective/s

This article reviews the published literature to establish the evidence for and against the Palaeolithic diet.

Discussion

The Palaeolithic diet remains controversial because of exaggerated claims for it by wellness bloggers and celebrity chefs, and the contentious evolutionary discordance hypothesis on which it is based. However, a number of underpowered trials have suggested there may be some benefit to the Palaeolithic diet, especially in weight loss and the correction of metabolic dysfunction. Further research is warranted to test these early findings. GPs should caution patients who are on the Palaeolithic diet about adequate calcium intake, especially those at higher risk of osteoporosis.

General practitioners (GPs) are commonly asked about popular diets. Fad diets come and go, some gaining more traction within the public sphere than others. One of the most controversial diets in recent times is the Palaeolithic diet, otherwise known as the Stone Age diet, or simply as Paleo.

Even without controversy, the Palaeolithic diet has been increasing in popularity over the past few years. The diet has been the subject of intense criticism by health professionals because of wellness bloggers’ and celebrity chefs’ exaggerated claims about its purported effects – for example, that the Palaeolithic diet could prevent or cure polycystic ovary syndrome, autism, mental illness, dementia and obesity.1

Does the published medical literature support the vast and extravagant claims made by the Palaeolithic diet’s celebrity proponents? Should GPs recommend the Palaeolithic diets to their patients, or caution them? This article seeks to review the published clinical research on the Palaeolithic diet.

Why Paleo? The rationale for the Palaeolithic diet

The rationale for the Palaeolithic diet stems from the evolutionary discordance hypothesis – that human evolution ceased 10,000 years ago, and our Stone Age genetics are ill-equipped to cope with our modern diet and lifestyle, leading to the ‘diseases of civilisation’.2–8 Thus, only foods that were available to hunter–gatherer groups are optimal for human health – ‘Could I eat this if I were naked with a sharp stick on the savanna?’.9 Therefore, meat, fruit and vegetables are acceptable, but grains and dairy products are not.10

Such views have drawn criticism from anthropologists, who argue that there is no blanket prescription of an evolutionarily appropriate diet, but rather that human eating habits are primarily learned through behavioural, social and physiological mechanisms.11 Other commentators have noted that the claims of the Palaeolithic diet are unsupported by scientific and historical evidence.12 The Palaeolithic diet’s anthropological validity notwithstanding, is there scientific support of the various health claims made of it? Pragmatically speaking, is a diet sans dairy and refined carbohydrates beneficial, even if it is not historically accurate?

Published evidence on the Palaeolithic diet

While proponents of the Palaeolithic diet claim that it is evidence-based, there are only a limited number of controlled clinical trials comparing the Palaeolithic diet to accepted diets such as the diabetic or Mediterranean diets (Table 1).

In 2007, Lindeberg et al performed a randomised controlled trial of the Palaeolithic versus Mediterranean-like diet in 29 patients with ischaemic heart disease and impaired glucose metabolism over 12 weeks. Both groups lost approximately the same amount of weight; however, the Palaeolithic group showed a significantly decreased waist circumference and improved glucose sensitivity.13 In 2009, Jönsson et al expanded on the study by Lindeberg et al. They published a randomised crossover pilot study of 13 patients with type 2 diabetes, randomised to either the Palaeolithic or diabetic-like diet over two consecutive three-month periods. Compared with patients on the diabetic-like diet, patients on the Palaeolithic diet showed improved HbA1c, diastolic blood pressure, lipid profile, weight and waist circumference, and no statistically significant change in C-reactive protein (CRP).14

Osterdahl and colleagues published a pilot study in 2008, in which 14 healthy volunteers were placed on the Palaeolithic diet over the course of three weeks. Six participants gave a complete dietary assessment. Across all participants, there was a significant mean weight loss of 2.3 kg over the three weeks and a mean decrease in waist circumference by 0.5 cm. Systolic blood pressure improved slightly and there was a stark rise in CRP, although it did not reach significance. The authors noted that the Palaeolithic diet was significantly lower in calcium compared to the subjects’ pre-study diet.15

Frassetto et al performed a metabolically controlled study in 2009 in nine non-obese, sedentary, healthy volunteers, comparing the Palaeolithic diet to their usual diet. The Palaeolithic diet led to significant reductions in blood pressure with improved arterial distensibility, insulin sensitivity and plasma lipids, all unrelated to body weight.16

In 2013, Jönsson et al studied the satiety of the Palaeolithic diet, compared with the diabetic diet, in a randomised crossover trial of 13 patients with type 2 diabetes. The Palaeolithic diet resulted in greater satiety quotients for energy, energy density and glycaemic load per meal. While the Palaeolithic diet was more satiating per calorie than the diabetic diet, they also noted that it was difficult to adhere to.17

In 2014, Boers et al compared the Palaeolithic diet with an isoenergetic, healthy control diet based on Dutch Health Council guidelines in 32 subjects with metabolic syndrome. The Palaeolithic diet resulted in lower systolic and diastolic blood pressure, and improved plasma lipid profile. Despite both diet arms being isocaloric, bodyweight decreased in the Palaeolithic group, compared with the reference (–1.32 kg; P = 0.012). No significant difference was found in intestinal permeability, inflammation and salivary cortisol as secondary outcome measures.18

Whalen et al in 2014 used data collected as part of a previous case-controlled research program at the University of Minnesota Cancer Prevention Research Unit between April 1991 and April 1994 to analyse the incidence of colorectal polyps versus the diet history given on a standardised dietary questionnaire. They found that for both the Palaeolithic and Mediterranean diets, there was no statistically significant change in risk.19

Mellberg et al published a longer term trial on the Palaeolithic diet in 2014. Their study was a randomised controlled trial of 70 women who were obese and post-menopausal, and they compared the Palaeolithic diet to a reference diet based on the Nordic Nutrition Recommendations over a two-year period. The end points were body fat percentage calculated by dual-energy X-ray absorptiometry (DEXA) scan, and the level of metabolic markers. The Palaeolithic group lost significantly more weight than the group on the reference diet at six months, although this was not sustained at the 24-month mark. The Palaeolithic diet group lost more body fat and lean tissue than the reference group. Both groups showed similar improvements in blood pressure, CRP and cholesterol, whereas there were no changes in fasting glucose and insulin.20

In a double-blind randomised controlled trial of 24 healthy male volunteers in 2015, Bligh et al compared the acute satiety and gut hormone responses of two Palaeolithic-type meals with a reference meal based on the World Health Organization’s Preparation and use of food-based dietary guidelines. Both Palaeolithic meals were predominantly plant based. The first Palaeolithic meal was based on estimated range ratios for protein and fat that was considered typical of hunter–gatherers, and contained no cereals or dairy products. The second Palaeolithic meal was made with identical plant-based ingredients to the first Palaeolithic meal, but normalised to the reference meal for caloric and macronutrient equivalence. There was no significant difference in the response of glucose and insulin between the meals.21

Reconciling the research

Looking at the studies as a whole, the Palaeolithic diet was often associated with increased satiety, independent of caloric or macronutrient composition, along with improvements in body weight, waist circumference, blood pressure and lipid profiles. However, the studies were short, heterogeneous in design and underpowered. The strongest of the studies was by Mellburg et al, who showed no long-term differences between participants on the Palaeolithic diet and those on the control at 24 months.20

In the studies that measured inflammatory markers, there was no significant difference as a result of consuming the Palaeolithic diet. Adherence and palatability were common issues raised about the Palaeolithic diet. Some studies reported improvements in plasma glucose or other markers of glycaemic control,10,14,16 though some did not,20,21 including the study of Bligh et al, which was a high-quality, laboratory-controlled study. It showed no significant difference in glucose and insulin levels for the Palaeolithic diet, compared with their reference meal.21

Other factors should be considered when thinking of the Palaeolithic diet in the broader patient context. Modelling of the cost of the Palaeolithic diet suggests that it is approximately 10% more expensive than an essential diet of similar nutritional value, which may limit the Palaeolithic diet’s usefulness for those on a low income.22 Calcium deficiency also remains a significant issue with the Palaeolithic diet; the study by Osterdahl et al in 2008 showed that the calcium intake of the Paleo diet was about 50% of the recommended dietary intake.15 Uncorrected, this could increase a patient’s risk of osteoporosis.23 Patients on the Palaeolithic diet should be referred to an accredited practising dietitian for individualised medical nutrition therapy (Table 2).

Table 2. Comparison of the current Australian dietary guidelines recommendations24 with the Palaeolithic diet15

Australian dietary guidelines

Palaeolithic diet

Enjoy a wide variety of nutritious foods from the following five groups every day

Plenty of vegetables, including different types and colours, and legumes/beans

Milk, yoghurt, cheese and/or their alternatives, mostly reduced fat (reduced fat milks are not suitable for children younger than two years)

All dairy products prohibited

Drink plenty of water

Ad libitum water (mineral water allowed if tap water unavailable)

Overall, conclusions about the effectiveness of the Palaeolithic diet should be considered cautiously. Positive findings should be tempered by the lack of power of these studies, which were limited by their small numbers, heterogeneity and short duration. Nevertheless, there appears to be enough evidence to warrant further consideration of the Palaeolithic diet as a potential dietary option in the management of metabolic diseases. Larger independent trials with consistent methodology and longer duration are required to confirm the initial promise in these early studies. Claims that the Palaeolithic diet could treat or prevent conditions such as autism, dementia and mental illness are not supported by clinical research.

Conclusion

The Palaeolithic diet is currently over-hyped and under-researched. While the claims made by its celebrity proponents are not supported by current evidence, the Palaeolithic diet may be of benefit in the management of various metabolic derangements. Further research is warranted to test these early findings. GPs should caution patients on the Palaeolithic diet about adequate calcium intake, especially those at higher risk of osteoporosis.

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03 December 2016 01:35

Re: Cutting through the Paleo hype: The evidence for the Palaeolithic diet

Owen Bruhn

OHS Pratcitioner

Comment as a private individual

It is good to see that a widely read reputable journal and author is discussing the paleolithic diet and reviewing it. I'd like to make a series of points really aimed at helping readers understand the paleo like "lifestyle" as it is more a lifestyle than a diet.

In hunter gather times (modern or ancient) our ancestors did not work as such they "exercised" outdoors for long periods each day hunting and gathering food. Typically hunter gathers trek to the food location, the work involved in getting the food (digging, using hunting tools, sprint to chase pray etc) and then carrying it back to the camp. Whilst some snacking may occur on the trek\trail food is taken back to camp and eaten there in the second half of the day. Most hunter gatherers eat their prey "top to tail" including organ meats etc. So the meal pattern tends to be smallish snacks during the day with the main meal at night time. Typically, hunter gatherers will also spend time in play (both social and physical), social activities including dance.

So what are the lifestyle factors:
- meal timing - main meal in second half of day. Occasional deficits in food available for consumption due to unavailability - not extreme chronic calorific deficit but a meal missed here and there but sufficient nutrients to maintain BMI in 20-25 range.
-seasonal nature of the diet. In nature food available varies over the year. In the case of plants there may be a narrow window of weeks or so in which the particular food is available.
- nutrient profile - there is no single one rather their are ranges. Food available at the equator differs from what the traditional eskimo eats. However, overall the diet tends to contain more protein, less carb and more fat than western diets. The balance of omega 3:6 is in favour of the 3's due to an absence of seed oil and eating of grass fed meat etc. Meat eaten tends to contain a little more salt than the western diet due to an absence of modern butchering techniques (ie less removal of blood). However, salt consumption still remains low compared to the western diet - early papers on human sodium requirement were actually based on work done on the Yanomamo hunter gatherers of South America. Organ meats and cartilagenous cuts are also eaten which increases the amount of collagenous gelatin eaten as well as providing higher levels of various micronutrients than muscle. With the proliferation of macro- micro- nutrient in food analysing software and web sites it is very easy to model the effect of a paleo like diet I did this out of interest when I got access to such software nearly 10 years or so ago and and found that I was getting sufficient quantities of all nutrients except vitamin D.

Not generally eaten on modern pure paleo like diet: dairy products, seed oils and cereal grains, refined sugar, potatoes, legumes (beans and peanuts). A review of the large literature will identify that these foods contain significant amounts of anti-nutrients. Gluten and gliadin of wheat are well known as are the poisonings that have occurred from eating green potatoes. Salt (sodium chloride) is also not added to foods. [NB a personal practice of mine is to lightly salt meals during hot spells especially if physical activity has\is to occur to reflect that my meat has the blood removed by the meat processor. Fish are exsanguinated to a far less extent and contain more salt).
-water drunk by hunter gathers is not demineralised like that drunk from the water systems in modern society. It is difficult to estimate the actual contributions of minerals to a paleo diet from drinking mineralised water as the quantities and range of minerals varies. Some mineral waters contain unusually high quantities of less common mineral springs they are derived from eg lithium, selenium etc. Some magnesium may be derived from natural waters depending on the mineral springs the water originates from. Similarly, clay and soil eating is known to occur in various hunter gatherer groups and it may be a way of topping up minerals (magnesium) although this is by no means certain.
- light levels during day - UVB during the day due to time spent in sun wearing comparatively little clothing. So, vitamin D serum levels are comparable to outdoor workers using minimal sun protection. Without diverging into an exhaustive discussion of the benefits of vitamin D it is noted that optimum vitamin D levels mean better calcium uptake. Optimum vitamin K2 means better transport of calcium to where it needs to go. Further, chewing on bone and cartilage, extracting bone marrow etc also mean more of a contribution of dietary calcium from the forms found in bone and cartilage per se.
-night time - Absence of lighting other than fire light means a shift in the light spectrum from blue to red. In pre-industrial times the sleep cycles tended to be biphasic (still recorded in literature as first and second watch).
-extended family rather than nuclear family with the social support needed to ensure survival. Older HGs were valued for their knowledge and experience.
- Physical activity - mixed varying training regime. Some strength training, some endurance training with plenty of general movement sprinkled through the day. Walk to food and back to camp was up to 5km or so a day. Camp tended to be moved if the distance increased. Camp had to be moved as prey and in ground plant food stocks were depleted or due seasonal changes. Effort in hunter gather times , unlike modern exercise regimes, was just sufficient to get the job efficiently done. Always holding back if possible. It is only have been in desparate situations that a HG, or any wild animal, will go all out.
Healthy hunter gatherers typically have excellent postural alignment and are barefoot. Modern humans grow up wearing shoes and typically healthy modern humans have poorer postural alignment. Barefoot activity has become popular, however, going barefoot in public environments is not without hazard due to nails, glass, needlesticks etc and prudence would dictate than minimalist shoes are worn. Further, increasing physical activity without have regard to any prehabilitation postural alignment will likely result in injury and a portion of any physical activity program should include Prehabilitation to prevent acute or chronic injury from occurring.
Stress and spirit - HGs typically have chunks of time spent in play, social and spiritual activity. Outlets were in tool making, decorations, the activities of food gathering including the hunt for men. Survival depended upon relying upon others and so the social forces tended to be highly cohesive and disputes rare with the mobility and lower population density permitting a split to occur if a serious dispute occurred. One of the parties (& mate) might then joint another band or start setting up their own extended family band.
Chunks of time were spent in the quiet of "being together with", reverie during contemplation of nature and during religious rituals. Some modern paleo practitioners utilise various types of meditation with one type, stillness Meditation, "developed" in Australia by Ainslie Meares being favoured by some - in stillness meditation the body relaxes, the mind relaxes, thoughts slow and become still. It would seem that this may be analagous to what happens with hunter gathers with spontaneous reverie or day dreaming occurring during "safe" times on a regular daily basis. It is noted that their are several types of meditation (about 6 categories) which may result in different mental states. A quieting of the mind with little or no thought, little or no emotion and little or no sensation is the simplest type. This effortless quietening may be akin to mental sleep whilst retaining consciousness.
The list above is not an exhaustive template but it is hoped to make several points:
- there is no one paleo diet but there are ranges (types and amounts of foods) that will fall within such a diet.
- it is more than a diet - it is a lifestyle template.

It is important to realise that it is all of these things together which need to occur. In modern science we dissect out individual factors. We tend to specialise as we learn more depth.

In doing these things we can lose the overview - whether we are paleo or conventional in our views. We should strive to obtain the best available evidence that is in accord with principles of biology but we should also recall that absolute proof may be difficult to obtain eg it took several hundred years to prove tobacco smoking caused great harm. It has taken perhaps 50 years to adequately prove the dangers of refined sugar whether in food or drink - the dose makes the response - refined sugar is pure sugar whereas foods in nature contain far less eg fruit and veg 1-20pc approx. fruits are seasonal (ie time frame restricts availability). In modern times people can buy more sweets, soft drinks than they can eat all year around. Similar arguments can be identified for the other factors discussed above. The key is using the pieces of the jig saw to sketch out the overview and do our best to fill in the gaps using principles of biology and constructive discussion so that we can all pick up the best new ideas, avoid poor new ones and avoid throwing out useful ones that can still serve us well. I still use seat belts although I'd rather walk if I can. If I can't then park the car a short distance away to design in a short walk to supplement my own physical health based fitness activities.

Bibliography
Below in no particular order is a list of books which contain information relevant to the discussion above.
The Paleo Diet by Loren Cordain. (Cordain and his students have done much of the original work on the Paleo Diet. His web site the Paleo Diet also has most of his published papers in peer reviewed journals - including one on an analysis of macronutrient ratios of historic and modern hunter gathers scattered from the equator to the north pole)
The biology of civilisation by Stephen Boyden. (An Australian Scientist provides a general overview of several aspects of the topic)
The Old Way by Elizabeth Marshall. (about the Kung! people of Africa around time of early contact with modern humans, their are also ethonographic atlases and a huge literature in the anthropology area.)
Nutrition and Physical Degeneration by Weston A Price. (The American Dentist who visited many areas in the world in the 1930s and documented side by side groups of people living traditional and modern modes of existence. Some of comparison groups are of traditional agricultural eating patterns rather than hunter gathers)
Strange Places and Simple Truths by Ainslie Meares (A Melbourne Psychiatrist discusses his travels in the 1950-1960s researching restful alternative states of consciousness). Meares' outlined his relaxing meditation in another book - The Wealth Within).
At Day's Close: Night in Times Past by A. Roger Ekirc. (Review civilisation's recorded history of sleep patterns etc).
The Primal Blueprint by Mark Sisson ( Sisson attempts outlines a general template discussed above which he calls the Primal Blueprint).
Pete Egoscue. The Egoscue Method of Health though Motion. (Egoscue's first book written in 1992 on the relationship between posture and function and improvement of function by realigning posture towards the human design template. Egoscue has written several other books ranging from extremely gentle exercises for damaged people through to his (more advanced) outdoor obstacle like course exercise programs (aka the Patch).

Competing Interests: I have Graduate Diplomas in Occupational Hygiene and Ergonomics, have been on a paleo like diet and lifestyle template for many years, am certificated in the Primal Blueprint, use the Egoscue method and practice Meares Stillness Meditation. I will leave the reader to decide whether or not these are conflicts of interest.

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